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FreeBSD-SA-20:33.openssl                                    Security Advisory
                                                          The FreeBSD Project

Topic:          OpenSSL NULL pointer de-reference

Category:       contrib
Module:         openssl
Announced:      2020-12-08
Affects:        All supported versions of FreeBSD.
Corrected:      2020-12-08 18:28:49 UTC (stable/12, 12.2-STABLE)
                2020-12-08 19:10:40 UTC (releng/12.2, 12.2-RELEASE-p2)
                2020-12-08 19:10:40 UTC (releng/12.1, 12.1-RELEASE-p12)
                2020-12-10 23:43:29 UTC (stable/11, 11.4-STABLE)
                2020-12-14 21:20:55 UTC (releng/11.4, 11.4-RELEASE-p6)
CVE Name:       CVE-2020-1971

Note: The OpenSSL project has published publicly available patches for
versions included in FreeBSD 12.x.  FreeBSD 11.x includes an older OpenSSL
version, and patches for that version from from the OpenSSL project are
only available to premium support contract holders.  This advisory includes
an independently-developed backport of the patch for FreeBSD 11.4.

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

0.   Revision History

v1.0 2020-12-08  Initial release.
v1.1 2020-12-14  Added FreeBSD 11.4 patch.

I.   Background

FreeBSD includes software from the OpenSSL Project.  The OpenSSL Project is a
collaborative effort to develop a robust, commercial-grade, full-featured
Open Source toolkit for the Transport Layer Security (TLS) protocol.  It is
also a general-purpose cryptography library.

II.  Problem Description

The X.509 GeneralName type is a generic type for representing different types
of names.  One of those name types is known as EDIPartyName.  OpenSSL
provides a function GENERAL_NAME_cmp which compares different instances of a
GENERAL_NAME to see if they are equal or not.  This function behaves
incorrectly when both GENERAL_NAMEs contain an EDIPARTYNAME.

III. Impact

An attacker who is able to control both items being compared can trigger a
NULL pointer dereference and a crash may occur leading to a possible denial
of service attack.  As an example, if an attacker can trick a client of
server to check a maliciously constructed certificate against a malicious CRL
could trigger the NULL dereference.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

Perform one of the following:

1) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 12.2, FreeBSD 12.1]
# fetch https://security.FreeBSD.org/patches/SA-20:33/openssl.patch
# fetch https://security.FreeBSD.org/patches/SA-20:33/openssl.patch.asc
# gpg --verify openssl.patch.asc

[FreeBSD 11.4]
# fetch https://security.FreeBSD.org/patches/SA-20:33/openssl.11.patch
# fetch https://security.FreeBSD.org/patches/SA-20:33/openssl.11.patch.asc
# gpg --verify openssl.11.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart all daemons that use the library, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r368459
releng/12.2/                                                      r368463
releng/12.1/                                                      r368463
stable/11/                                                        r368530
releng/11.4/                                                      r368643
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://www.openssl.org/news/secadv/20201208.txt>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-1971>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:33.openssl.asc>
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